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8950 



Bureau of Mines Information Circular/1983 



Fresnel Lens Blind Area Viewers 
for Improved Mine Equipment 
Safety and Productivity 




By Guy A. Johnson 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8950 

tl 

Fresnel Lens Blind Area Viewers 
for Improved Mine Equipment 
Safety and Productivity 

By Guy A. Johnson 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



Library of Congress Cataloging in Publication Data: 







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Johnson, Guy A 

Frcsnc] lens blind area viewers for improved mine equipment safety 
and productivity. 

(Information circular ; 8950) 

Includes bibliographical references. 

Supt. of Docs, no.: I 28.27:8950. 

1. Mining machinery — Blind-area viewers. 2. Kresnel lenses. 1. 
Title. II. Series: Information circular (United States. Bureau of Mines) ; 
8950. 



-m2&57U4- [TN345] 622s [622'.8] 83-15013 



CONTENTS 



Page 



Abstract 1 

Introduction 2 

Design, development , and debugging of first-generation prototype 5 

Second-generation, low-profile design 6 

Related work on collision protection of mine equipment 11 

Commercialization and cost-effectiveness analysis 13 

Summary 15 

ILLUSTRATIONS 

1. A 220-ton-capacity truck undergoing maintenance in an Arizona copper mine. 3 

2. Typical blind areas around a large haulage truck 3 

3. Maintenance vehicle run over by a large haulage truck 4 

4. Large front -end loader backing over a pickup truck 4 

5. Typical "whip" used in surface mines to warn haulage truck drivers of the 

presence of smaller vehicles 6 

6. Components of the improved visibility system for large haulage vehicles... 6 

7. Increased driver f ield-of-view with the improved system for large haulage 

t rucks 7 

8. Improved right-side visibility with the downward-looking blind area viewer 7 

9. Components of the first-generation fresnel lens blind area viewer 8 

10. In-mine, on-vehicle test of first-generation prototype hardware 8 

11. Design of second-generation blind area viewer 10 

12. Second-generation blind area viewer 10 

13. Mockup testing of the second-generation blind area viewer 11 

14. View through the second-generation blind area viewer during the mockup 

testing 11 

15. Initial in-mine testing of second-generation blind area viewers on a 170- 

ton-capacity truck 12 

16. On-truck. testing of three viewers 13 

17. Testing the viewer on the back of a large front-end loader 14 

18. View of a car through the blind area viewer on a large front-end loader... 14 

19. Close-in collision warning device 15 

20. Prototype CCTV rear-viewing system in an Arizona copper mine 15 

TABLES 

1. In-mine testing of the first-generation improved visibility system proto- 

type hardware 5 

2. In-mine testing of the second-generation, low-profile blind area viewers.. 9 



FRESNEL LENS BLIND AREA VIEWERS FOR IMPROVED MINE EQUIPMENT 
SAFETY AND PRODUCTIVITY 

By Guy A. Johnson 



ABSTRACT 

Combining contract and in-house research, the Bureau of Mines has de- 
veloped and in-mine-tested a novel device to improve the f ield-of-view 
of operators of off-highway mining equipment. This device utilizes a 
downward-looking, flat fresnel lens. The lens, plus louvers to reduce 
glare, is housed in a protective steel structure. The complete unit is 
called a blind area viewer. The viewer, when mounted on the right- 
front corner of the deck of most large haulage trucks, will increase a 
driver's direct f ield-of-view from about 35 pet (of where he/she has to 
drive) to about 80 pet. The improved visibility allows the driver to 
see possible collision hazards and roadway obstacles better, thus im- 
proving mine safety and increasing productivity. Economic analysis 
shows that the blind area viewers, which are now commercially avail- 
able, pay for themselves in about a month on a 170-ton-capacity truck. 
The viewers are also applicable to other large mining equipment, such 
as front-end loaders, draglines, and downhole drills, or any place 
where seeing around a corner would be advantageous, such as along con- 
veyor flights in processing plants during startups. 



Supervisory mining engineer, Twin Cities Research Center, Bureau of Mines, Minne- 



apolis, Minn. 



INTRODUCTION 



As mine haulage equipment becomes 
larger in order to increase productivity 
and cut costs, the driver's f ield-of-view 
becomes more restricted because the 
truck's cab is pushed back under the pro- 
tection of the truck box lip. Also, in 
order to increase maintenance efficiency, 
a great deal of ancillary equipment is 
installed on the truck's radiator deck, 
thereby further restricting the driver's 
view and increasing the hazard of mine 
vehicle collisions. Other problems, such 
as excessive tire wear and slow vehicle 
movement, can be related to the driver's 
inability to see clearly the haulage road 
and the loading and dumping areas. 

To help solve this growing problem of 
impaired visibility, the Bureau of Mines 
worked with mining officials, heavy 
equipment manufacturers , and personnel of 
the Mine Safety and Health Administration 
to develop and in-mine test reasonably 
priced, rugged hardware for retrofit on 
large haulage vehicles. One possible so- 
lution was to use closed-circuit televi- 
sion (CCTV) technology, but Bureau re- 
search indicated that although CCTV may 
help to reduce specific problems that oc- 
cur during backing up at high dump points 
(e.g., mountain tops), expensive mainte- 
nance is required in order for the system 
to be reliable in the harsh mining envi- 
ronment. Another option was to improve 
mirror technology. The use of larger 
convex mirrors provided a simple and good 
way to improve the rearview capability. 

2 Bureau of Mines. Improved Visibility 
Aids for Large Haulage Vehicles. Tech- 
nol. Transfer film, 1980, 14 min. 

Johnson, G. A. Improved Visibility 
System for Large Haulage Trucks. Pres. 
at 1980 Off-Highway Equipment Show, Mil- 
waukee, Wis. SAE preprint 800934, 17 
pp.; available from G. A. Johnson, Twin 
Cities Research Center, BuMines, Minne- 
apolis, Minn. 



However, the major hazard area of a 
vehicle — the right-front blind area — 
still existed. This led to the develop- 
ment of the fresnel lens blind area 
viewer. 2 

Although operators of today's huge 
equipment need improved f ield-of-view, it 
should be emphasized that smaller equip- 
ment can also use relevant technology. 
As an example, there is much congestion 
in many sand and gravel and crushed stone 
operations, especially those where the 
public has access to the pit and plant. 
A medium-sized front-end loader can eas- 
ily back over a street vehicle parked in 
its rear blind area. Installing fresnel 
lens blind area viewers on the rear of 
front-end loaders is proving very worth- 
while in such situations. Also, because 
there is much pedestrian traffic in ura- 
nium pits (for example, geologists di- 
recting the loaders to the highest grade 
material) , viewers are needed by even the 
small, 35-ton-capacity trucks. These 
trucks have a bad right-front blind area, 
and a driver, especially on a hard right 
turn, can easily be on top of in-pit per- 
sonnel before there is time to avoid 
them. 

Most of the references to mine equip- 
ment in this report target the sort of 
large haulage vehicles shown in figure 1, 
but their extensive blind areas (fig. 2) 
and resulting danger (as dramatized by 
the crushed maintenance vehicle in figure 
3) are typical of other large equipment 
such as front-end loaders (fig. 4). 

. Improved Visibility Systems. 

Paper in Surface Mine Truck Safety. Pro- 
ceedings: Bureau of Mines Technology 
Transfer Seminars, Minneapolis, Minn. , 
June 25, 1980, Birmingham, Ala., July 9, 
1980, and Tuscon, Ariz., July 24, 1980. 
BuMines IC 8828, 1980, pp. 22-39. 







. d#*. 



FIGURE 1, . A 220=ton-capacity truck undergoing maintenance in an Anzona copper mine, 



150 ton 




©I 





25ft; 



60 ft 



80 ft 



M 



Typical blind areas around a lege haulage truck 




Jt 



FIGURE 3. - Maintenance vehicle run over by a large haulage truck. 




FIGURE 4. - Large front=end loader backing over a pickup truck. 



DESIGN, DEVELOPMENT, AND DEBUGGING OF FIRST-GENERATION PROTOTYPE 



In 1976, the Bureau contracted with the 
Tracor MBA Corp. to study the visibility 
problem and outline solutions. This work 
was built on the successful development 
and testing of automatic fire protection 
systems for large haulage vehicles. It 
followed the philosophy that not only 
was laboratory work necessary, but the 
resulting equipment must also be sub- 
jected to in-mine, on-vehicle testing so 
as to properly debug the hardware and 
demonstrate its effectiveness. 

Simple solutions were evaluated, such 
as the extensive use of whiplike antennas 
to serve as warning devices (fig. 5), but 
only temporary attention was given to 
these flags by haulage truck drivers. 
The next step was to develop a family of 
devices that could be retrofitted to the 
haulage truck itself to improve the 
driver's f ield-of-view. This complete 
system, consisting of improved right- and 
left-hand mirrors , ruggedized closed- 
circuit television, and fresnel lens 
blind area viewers (fig. 6) , improved the 
driver's f ield-of-vision significantly 
(fig. 7). The most important component 



of the system was the front-right-mounted 
viewer. It allowed a direct view of a 
truck's most collision-prone area (fig. 
8) . The viewer combined the downward- 
looking ability of a flat fresnel lens 
(the grooves bend the light like a prism) 
with glare control louvers to keep in- 
coming light from blinding the driver 
(fig. 9). 

This first-generation improved system 
prototype was taken to Kaiser Steel's 
Eagle Mountain Mine near Palm Springs , 
Calif., in 1977 for a short-term test. 
This evaluation involved mounting three 
blind area viewers, a backup CCTV system, 
and improved mirrors on a 170-ton- 
capacity truck and operating the vehicle 
for 1 week (fig. 10). The success of 
this demonstration prompted the Bureau to 
subject the prototype hardware to long- 
term testing in three more mines in 1977 
and 1978 (the Decker Mine in Decker, 
Mont., the Erie Mine in Hoyt Lakes, 
Minn. , and the Belle Ayr Mine south of 
Gillette, Wyo.). Details of the testing 
are shown in table 1. 



TABLE 1. - In-mine testing of the first-generation improved visibility 
system prototype hardware 



Site 


Haulage truck 


Mine 


Comments 




capacity, tons 


type 




Eagle Mountain Mine, 


170 


Iron ore 


3 viewers were used on front-right 


Kaiser Steel Corp., 






side of vehicle for full cover- 


Eagle Mountain, Calif. 






age. Also, a first-generation 
CCTV was tried on back of truck. 


Erie Mine, 


100 


Taconite 


3 viewers, plus the CCTV and mir- 


Pickands Mather & Co., 






ror prototypes, were tried in 


Hoyt Lakes , Minn. 






this cold-weather environment. 


Belle Ayr Mine, 


120 


Coal 


3 viewers were tested on 2 trucks. 


AMAX Coal Co. , 








Gillette, Wyo. 








Decker Mine, 


120 


Coal. . .. 


Right- and left-hand prototypes, 


Peter Kewit Co. , 






plus the CCTV, were tested. 


Decker, Mont. 










FIGURE 5. ■= Typical "whip" used in surface 
mines to warn haulage truck drivers of the pres= 
ence of smaller vehicles. 



T V monitor 
Left rear- 




FIGURE 6. = Components of the improved vis- 
ibility system for large haulage vehicles. 



SECOND-GENERATION, LOW-PROFILE DESIGN 



The blind area viewers were the most 
viable component of the improved visibil- 
ity system, so further work was initiated 
to refine the hardware's design. Only 
two major modifications seemed to be 
needed. The first was to eliminate the 
upward-looking portion of the fresnel 
lens . It was originally thought that an 
"all around" (i.e., fisheye) picture 
through the viewer would help orient the 
driver, but experiments showed that elim- 
inating the top 3 in (i.e., the upward- 
angled portion) of the lens did not im- 
pair the vision. Instead, this reduced 
the size of the viewer and reduced the 
potential problem of sun glare in the 
early mornings and evenings. 

The second design modification was to 
add a hood on the rear of the lens to 
reduce backlighting (figs. 11-12). The 



redesigned viewer was then demonstrated 
at the contractor's facilities in San Ra- 
mon, Calif. Figure 13 shows a mockup of 
the front of a large haulage truck — note 
the position of the man with the hat 
standing in front of the truck mockup. 
Figure 14 shows the man as seen through 
the second-generation, low-profile blind 
area viewer. 

Besides the redesigning of the viewer 
to the low profile, additional in-mine 
testing was needed so the industry could 
more fully understand the many applica- 
tions of this unique device. To this 
end, an evaluation program was extended 
to various types of equipment in surface 
mines, stone quarries, coalpits, and ura- 
nium mines. Table 2 summarizes this 
work. 




FIGURE 7. - Increased driver field-of-view with the improved system for large haulage trucks. 



Area of visibility 
improvement 

Grade horizon 




FIGURE 8. - Improved right=side visibility with the downward-looking blind area viewer. 



Lens 
enclosure 



Rubber 
protector 




Mounting 
bracket 



Lens 
assembly 



Lens retainers with 
rubber molding 







Fresnel lens 
unit, 12 by Kin 

Safety glass 




Glare 

control 

louvers 



FIGURE 9, = Components of the first=generation fresnel lens blind area viewer. 




FIGURE 10. » ln=mine, on-vehicle test of first-generation prototype hardware (blind area viewers 
are on radiator deck). 



TABLE 2. - In-mine testing of the second-generation, low-profile blind area viewers 



Site 


Equipment 


Mine type 


Hardware tested and comments 


Eagel Mountain Mine, 


100- and 170-ton haulage 




First 3 viewers, then 1 far-right viewer, plus 


Kaiser Steel Corp., 


trucks. 




improved mirrors. 


Eagle Mountain, Calif. 








Erie Mine, 


3 100-ton haulage trucks.. 


Taconite. 


First 3 viewers, then 1 right-front viewer, 


Pickands Mather & Co., 






plus improved rearview mirror. 


Hoyt Lakes, Minn. 








Belle Ayr Mine, 






Viewers. All 3 viewers were used in the oper- 


AMAX Coal Co. , 






ation, as blowing dirt and snow often limited 


Gillette, Wyo. 






visibility. 


Minorca Mine, 




Taconite. 


1 right-front viewer, plus improved right- and 


Inland Steel Co. , 






left-hand mirrors. 


Virginia, Minn. 








Helena Quarry, 


50-ton truck and 2 12-yd 


Limestone 


1 far-right viewer on truck, as well as view- 


Vulcan Materials Corp., 


loaders. 


quarry. 


ers on back of 2 loaders that worked in the 


Birmingham, Ala. 






plant area for stockpile loadout. 
Successful. 


Cyprus Pima Mine, 




Copper. . . 


First 3 viewers, then 1 right-front viewer, 


Cyprus Mining Co., 






plus improved mirrors. 


Tucson, Ariz. 








Bear Creek Mine, 


120-ton haulage truck, 12- 


Uranium. . 


1 viewer on far-right side of each truck 


Kennecott Co. , 


yd front-end loader, and 




and on rear of loader. 


Casper, Wyo. 


35-ton haulage truck. 






Pinto Valley Mine, 




Copper. . . 


1 viewer on far right. Successful. 


Cities Service Co., 








Miami, Ariz. 








Coteau Mine, 




Lignite. . 


1 viewer, plus improved mirrors. Successful. 


North American Coal Corp., 




Beulah, N. Dak. 








Texas Quarry, 


2 120-ton trucks and 12-yd 




Viewers and mirrors. Successful. 2 blind 


Flintkote Stone, 


loader. 




area viewers were destroyed and the mine 


Hunt Valley, Md. 






wanted replacement units immediately. 


Glenrock Mine, 






2 viewers. Successful. 


Glenrock Coal Co., 








Glenrock, Wyo. 








National Steel Mine, 




Taconite. 


1 right-front viewer. Flood-lighting was 


Hanna Mining Co., 






tried successfully into the right-front 


Keewatin, Minn. 






blind area of the test truck. 


Brownies Creek Mine, 


2 85-ton haulage trucks... 




1 viewer on far-right side. Successful. 


Harbert Construction Co., 








Pineville, Ky. 








Highland Mine, 


100-ton haulage trucks.... 


Uranium. . 


Viewers and mirrors. Drivers did not like 


Exxon Minerals Co., 






viewers, as they had to clean the glass too 


Casper, Wyo. 






many times; they did like mirrors. 


Indianhead Mine, 


120-ton haulage truck and 


Lignite. . 


Viewers on truck and 1 mirror on shovel. 


North American Coal Corp., 


loading shovel. 




Successful. 


Beulah, N. Dak. 








Jackson County Mine, 






Viewers. The first viewers were damaged by 


Jackson County Iron Co., 






vehicle vibration; replacement units (prop- 


Inland Steel Corp. , 






erly installed) are now properly operating. 


Black River Falls, Wis. 








Mauricetown Quarry, 
Jessie Morie Co., 




Crushed 
stone. 


Viewers. Working well on back of small 
loaders. 




Mauricetown, N.J. 








Morenci Mine, 


2 100-ton haulage trucks.. 


Copper. . . 


Viewers and mirrors. Drivers like improved 


Phelps Dodge Corp., 






mirrors, but cleaning viewers is a problem. 


Morenci, Ariz. 









10 



Glare control head 



Tilt adjustment 



Mounting bracket 




Louvers 
(glare control) 

FIGURE 11, - Design of second-generation blind 
area viewer. 



Figures 15 and 16 show the second- 
generation hardware at the Eagle Mountain 
Mine in 1978. Three viewers were tried 
on the 170-ton truck to get the maximum 
f ield-of-view for the driver. After a 
few months of testing, comments from 
drivers led to a change in the layout and 
just the far right-front viewer was used 
instead of all three. This viewer cov- 
ered the most dangerous blind area and 
did not distract the driver's eyes as did 
the forward-looking viewers during truck 
movement. In fact, long-term use of this 
single viewer proved to be the most ac- 
ceptable, because drivers naturally turn 
their heads to that side when turning 
right and would look into the viewer. 
The arrow in figure 16 shows the optimum 
mounting location. 

Long-term testing of the low-profile 
hardware was also conducted on large 
front-end loaders (FEL). Figure 17 shows 
such an installation at the WIDCO coal 
mine in Centralia, Wash. Figure 18 gives 
the driver's view through the viewer. 




FIGURE 12. = Second=generation blind area viewer, 



11 




FIGURE 13. = Mockup testing of the second-generation blind area viewer. 




FIGURE 14.- View through the second*generation 
bl incl area viewer during the mockup testing. 



During in-pit loading the drivers did not 
use the viewer, but once they brought 
their loaders into the plant area, the 
ability to see the rear blind area was 
greatly appreciated. The mine has had a 
number of near misses because of the 
heavy foot traffic and congestion in the 
plant and maintenance shop areas. 

RELATED WORK ON COLLISION PROTECTION 
OF MINE EQUIPMENT 

The blind area viewer has been gaining 
wide acceptance by the mining industry, 
but it is only part of the solution to 
the problem of collision protection in 
surface mines. The viewer is simple and 
relatively maintenance free (it needs oc- 
casional cleaning as does any vehicle's 
mirror), and it is inexpensive, thus cost 
effective. Current Bureau work is now 
concentrating on answering two related 
questions: (1) What motivates a driver 
to look in the viewer so he/she can take 
action to avoid a potential accident, and 



12 




FIGURE 15 c = Initial in=mine testing of second=generation blind area viewers (indicated by arrows) 
on a 170=ton=capacity truck, 



(2) what might prevent 
backing-up collision. 



the close-in, 



The improved right- and left-hand mir- 
rors recently developed by the Bureau 
allow much better rear vision, but small 
vehicles still get into a truck's rear 
blind area. The improved left-hand mir- 
ror is a quick-change, 20- by 10-in flat 
mirror, and the right-hand mirror is a 
novel 30-in-radius , rectangular-convex 
device. Both mirrors, plus the right- 
front mounted viewer, are recommended for 
use on trucks today and are commercially 
available. Electronic devices could be 
used to warn drivers of potential colli- 
sions, but while many radar, infrared, or 
sonic devices are small and inexpensive 
enough for on-vehicle use, most are not 
rugged enough for the harsh mining envi- 
ronment. An electronic system for com- 
plete collision protection is still a few 



years away, but close-in sonic detectors, 
now being modified by the Bureau (fig. 
19), seem to have great potential. This 
is especially true when the detector is 
combined with the blind area viewer and a 
voice warning system in the cab, to warn 
the driver that something is either in or 
approaching the blind side. Laboratory 
work on such hardware is now being con- 
ducted by the Bureau. 

A direct view of the rear ground area 
and dump point or beam is possible via 
CCTV hardware. The Bureau is currently 
evaluating this alternative (fig. 20), 
but such systems are relatively expensive 
and require extensive maintenance. Mines 
with very hazardous dumping conditions 
(such as a high waste dump over the side 
of a mountain) are cooperating with the 
Bureau to perfect CCTV-lighting technol- 
ogy. As a result of this work, the price 



13 




FIGURE 16. = On-truck testing of three viewers. Optimum location of a single viewer on a large 
truck is at the right front, as indicated by arrow. 

of a reliable system has dropped from design and in-mine testing of automated 



about $60,000 to about $5,000 per vehi- 
cle. Future work with ruggedized CCTV 
applications will use newly developed 
hardware in the $500 to $1,000 range. 
Other longer term work involves the 



backup warning devices and driver alert- 
ness monitors, plus the creation and 
evaluation of novel haulage truck designs 
that eliminate many of the inherent dan- 
gers in today's equipment. 



COMMERCIALIZATION AND COST-EFFECTIVENESS ANALYSIS 



Since May 1981, the Tracor MBA Corp. of 
San Ramon, Calif., has been marketing 
both the low-profile blind area viewer 
and the improved mirrors. About 1,000 
units have been sold, many to foreign 
countries. The pricing of the hardware 
varies according to the quantity ordered. 



Assuming one right-front-mounted blind 
area viewer on medium-sized trucks (i.e., 
up to 150-ton capacity) and one far- 
right-side plus a right-front viewer 
for vehicles in the 170-ton-plus class, 
a payback period of about 1 month is 



14 




FIGURE 17. - Testing the viewer on the back of a large front=end loader. 

obtained. This calculation assumes a 
cost of $500 per viewer and considers 
such factors as an ownership and operat- 
ing cost of $175 to $200 per hour for 
a 170-ton truck and only a 1-pct improve- 
ment in haulage truck productivity 
because of better driver vision (a real- 
istic figure based on the Bureau's in- 
mine test program). One percent of $200 
is $2 per hour; thus the viewer cost 
installed — $1,000 — is returned in 20 
working days. 

Tracor MBA will send marketing informa- 
tion to any interested party. A number 
of mines are now ordering new vehicles 
with viewers already installed; thus, 
retrofit action is not needed. A new 
company, Optical Science Group of Peta- 
luma, Calif., initiated a marketing ef- 
fort in late 1982 to sell a smaller ver- 
sion of a fresnel lens viewer called 
Safe-T-Site, which costs substantially 
less than $500 per unit. 




FIGURE 18. = View of a car through the blind 
area viewer on a large front-end loader. 



15 



Sonar coverage area 



Sonar coverage area 




FIGURE 19. - Close-in collision warning device. 




FIGURE 20. - Prototype CCTV rear-viewing system in an Arizona copper mine. 

SUMMARY 



Fresnel lens blind area viewers improve 
not only mine safety but also equipment 
productivity. This novel device was de- 
veloped and in-mine-tested by the Bureau 
through complementary in-house and con- 
tract R&D. It is commercially available 
and has a payback period of about 1 
month. Blind area viewers are applicable 
not only to haulage trucks, but also to 



large front-end loaders, downhole drills, 
draglines, power shovels, etc. During 
in-mine testing of prototype viewers, at 
mines where the viewers were installed 
properly and drivers were told what to 
expect, there was a positive response 
from the drivers and an estimated 1- to 
5-pct improvement in maneuverability. 

INT.-BU.OF MINES, PGH., PA. 27130 



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